This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A062779 #13 Jan 04 2025 09:54:55
%S A062779 0,4,96,4320,322560,36288000,5748019200,1220496076800,334764638208000,
%T A062779 115242726703104000,48658040163532800000,24728016011107368960000,
%U A062779 14890761641597746544640000,10485577989291746525184000000
%N A062779 a(n) = 2*n*(2*n)!.
%D A062779 Jerome Spanier and Keith B. Oldham, "Atlas of Functions", Hemisphere Publishing Corp., 1987, chapter 38, equation 38:6:2 at page 364.
%H A062779 Wikipedia, <a href="https://en.wikipedia.org/wiki/Trigonometric_integral#Cosine_integral">Cosine integral</a>.
%H A062779 Wikipedia, <a href="https://en.wikipedia.org/wiki/Trigonometric_integral#Hyperbolic_cosine_integral">Hyperbolic cosine integral</a>.
%F A062779 From _Amiram Eldar_, Feb 14 2021: (Start)
%F A062779 a(n) = A001563(2*n) = 2*n*A010050(n).
%F A062779 Sum_{n>=1} 1/a(n) = Chi(1) - gamma = A099284 - A001620, where Chi(x) is the hyperbolic cosine integral
%F A062779 Sum_{n>=1} (-1)^(n+1)/a(n) = gamma - Ci(1) = A001620 - A099282, where Ci(x) is the cosine integral. (End)
%t A062779 a[n_] := 2*n*(2*n)!; Array[a, 14, 0] (* _Amiram Eldar_, Feb 14 2021 *)
%o A062779 (PARI) for(n=0,22,print((2*n)*(2*n)!))
%Y A062779 Cf. A001563, A001620, A010050, A099282, A099284.
%K A062779 easy,nonn
%O A062779 0,2
%A A062779 _Jason Earls_, Jul 18 2001